Centrifugal fan and method for cleaning thereof

ABSTRACT

The invention relates to a centrifugal fan, comprising an impeller and a housing enclosing the impeller with a medium supply opening and a medium discharge opening, wherein the housing connects the medium supply opening and the medium discharge opening, whereby the housing is adjustable between an open state, in which at least one circumference of the impeller and/or the inside of the housing is substantially completely accessible and a closed condition, in which the housing connects the medium supply opening and the medium discharge opening to a medium-permeable and airtight manner. 
     The invention also relates to a procedure for cleaning such a fan, comprising the steps:
         (a) setting the fan housing to the open state, whereby the circumference of the impeller and/or the inside of the housing are substantially completely accessible;   (b) cleaning of the impeller and/or of the inside of the housing;   (c) setting of the housing back to the closed state, whereby the housing connects the medium supply opening and the medium discharge opening to a medium-permeable and air-tight manner.

BACKGROUND

The invention relates to a centrifugal fan, comprising an impeller and a housing enclosing at least the impeller with a medium supply opening and a medium discharge opening, wherein the housing connects the medium supply opening and the medium discharge opening to a medium-permeable and airtight one.

Such centrifugal fans are known per se, and can for instance be used for moving, for example, ambient air in industry, more particularly in the food industry, for example. Due to growing hygiene requirements, among other things, centrifugal fans of the type described above must be regularly and/or thoroughly cleaned. The cleaning of known centrifugal fans is, however, cumbersome and/or perhaps at least in part impossible because certain parts of such fans are not accessible.

There is therefore a need for a centrifugal fan that is easier and/or better to clean than existing centrifugal fans.

The invention meets this need by providing a centrifugal fan of the type mentioned above with the characteristic that the housing is adjustable to an open state, whereby at least one circumference of the impeller and/or the interior of the housing is essentially fully accessible and back to its closed state, whereby the housing connects the media inlet opening and the media outlet with each other in a medium-permeable and airtight manner.

SUMMARY

A housing which is adjustable to an open state can offer the advantage that in that open state a relatively large part of the fan and in any case the circumference of the impeller and/or the inside of the housing is accessible for cleaning.

In case the entire circumference of the impeller is accessible, the impeller can be cleaned in its entirety from the periphery to a central part of the impeller, especially without the need to rotate the impeller during cleaning or in between cleaning. If the inside of the housing is fully accessible, the entire inside of the housing can be cleaned properly. As a result, the invention provides a fan which is hygienic in use and which, moreover, can be closed airtight after cleaning.

It may be particularly advantageous that the centrifugal fan can be set back to its closed condition, in which the housing connects the medium supply opening and the medium discharge opening to a medium-permeable and air-tight manner, such that the centrifugal fan can then build up pressure in the housing when in use, even after it has been opened once to clean the inside of the fan.

In addition, an airtight seal of the housing can be more hygienic.

The fact that the housing connects the medium supply opening and the medium discharge opening to each other in airtight manner can mean that the housing on the medium supply opening and the medium discharge opening is air-tight. In other words, the housing itself is not airtight, because medium can be supplied and discharged through the medium supply opening and the medium discharge opening, but the housing in the medium-permeable path between the medium supply opening and the medium discharge opening is airtight. In particular, in use of the fan medium supplied via the medium supply opening, can only leave the housing via the medium discharge opening, because the housing is air-tight for the rest.

In particular, the housing can comprise no or few corners. A housing with no or few corners can be cleaned better and offers with a frequent, for example daily cleaning, no or only limited possibility for bacterial growth.

In an embodiment of the centrifugal fan according to the invention, the impeller is rotatable about a rotational axis, whereby the housing comprises a first housing part arranged on a first side of the impeller perpendicular to the rotational axis and having a second housing part arranged on a second side of the impeller perpendicular to the rotational axis, whereby the first housing part and/or the second housing part comprises a circumferential wall which in the closed state of the centrifugal fan connects the first housing part and the second housing part directly or indirectly in airtight manner, whereby the first housing part and the second housing part are separable from each other for adjusting the centrifugal fan to its open state.

By splitting the housing into a first housing part and a second housing part, a centrifugal fan can be created which can make a relatively large part of the impeller and / or the inside of the housing accessible for cleaning.

The rotational axis is an imaginary axis around which the impeller rotates.

In another embodiment of the centrifugal fan according to the invention the first housing part and the second housing part are mutually displaceable, preferably hinged, connected to each other.

An advantage of connecting the housing parts movably relative to each other may be that the housing parts in an open state can release a large part of at least the circumference of the impeller and/or the housing, while it is not necessary to have one of the housing parts completely removed and stored elsewhere during cleaning.

In yet another embodiment of the centrifugal fan according to the invention, the first housing part and the second housing part are pivotally connected to each other by means of a hinge, wherein the hinge is connected to the first housing part and/or the second housing part by means of adjustable fastening means.

The adjustable fastening means can be used to align the two housing parts, and can in this way contribute to an airtight seal in the closed state of the centrifugal fan.

Aligning the two housing parts with each other can mean that the two housing parts are registered with each other and/or that the two housing parts are positioned coaxially with respect to each other and possibly the impeller and/or that the two housing parts are positioned with respect to each other in such a way that any sealants may be used, such as a sealing ring specified below and/or connectors specified below working together and being attached to the enclosure parts may contribute to the airtight sealing of the housing.

The adjustable fastening means can for instance be arranged to adjust the position and/or orientation of the hinge relative to the first housing part or the second housing part. In particular, the adjustable fastening means can be arranged to adjust the position and/or orientation of the hinge in one, two or three different orthogonal directions with respect to the first housing part and/or the second housing part.

In yet another embodiment of the centrifugal fan according to the invention, the first housing part and the second housing part are provided with mutually cooperating connecting means for connecting the first housing part and the second housing part together.

The cooperating connection means can contribute to airtight connection of the two housing parts in the closed state of the centrifugal fan.

In yet another embodiment of the centrifugal fan according to the invention, the cooperating connecting means comprise at least one clamp, whereby at least one clamp is provided with a first clamping part which is fixedly connected to one of the first housing part and the second housing part, and a second clamping part detachably connectable to the other of the first housing part and the second housing part, wherein in the open state of the centrifugal fan the second clamping part is not connected to the other of the first housing part and the second housing part, and in the closed state of the centrifugal fan the second clamping part is connected to the other of the first housing part and the second housing part, and the clamp clamps the first housing part and the second housing part towards each other by means of the first clamping part and the second clamping part.

The at least one clamp may contribute to an airtight seal of the housing in the closed state of the centrifugal fan by connecting the two housing parts together by clamping them together with a clamping force, wherein, for setting the centrifugal fan to its open state, the clamping force can be released or at least reduced by the at least one clamp, where after the second clamping part can be detached from the other housing part so as to disconnect the connection between the two housing parts and the centrifugal fan can be opened.

In particular, the clamping parts can engage on a part of the outer surface, for instance on an outer circumferential edge zone or a lip extending from the outer circumferential edge zone of the first housing part and/or the second housing part.

In still another embodiment of the centrifugal fan according to the invention, a distance between the first clamping part and the second clamping part of the clamp is adjustable for setting a clamping force with which the clamp clamps the first housing part and the second housing part towards each other in the closed state of the centrifugal fan, preferably by means of an adjusting nut.

Because the clamping force of the at least one clamp is adjustable, it is easy to compensate for any deformations and/or imperfections of the housing in order to still contribute to an airtight seal of the housing despite the deformations and/or imperfections.

For example, several clamps can be provided, wherein the clamping force of the different clamps can be chosen individually and wherein the clamping force of the different clamps can be the same or different.

In another embodiment of the centrifugal fan according to the invention, the at least one clamp is equipped with a spring element which is designed for supplying a clamping force by means of preloading a clamping force for clamping the first housing part and the second housing part towards each other, wherein the spring element is preferably a saucer spring.

The spring element may provide a clamping force even if the adjustment of the clamp is not perfect and/or it may prevent the clamping force from being set too high, which may cause damage to the clamp and/or the fan. Furthermore, the spring element can provide the clamp with a small clearance, which can be used to connect and disconnect the second clamping part of the housing.

Preferably, the spring element is designed as a saucer spring, whereby the saucer spring can be arranged on a side of the optional adjusting nut facing the clamping member.

In yet another embodiment of the centrifugal fan according to the invention, the second clamping part comprises a securing element rotatable about a rotational axis, whereby the securing element in a closed state of the centrifugal fan fits tightly against the other of the first housing part and the second housing part for clamping the first housing part and the second housing part towards each other, whereby the securing element comprises a first surface part remote with a first distance from the rotational axis and a second surface part remote with a second distance from the rotational axis, whereby the first distance being smaller than the second distance, whereby the first surface part and second surface part can be alternately be directed towards the other of the first housing part and the second housing part by rotation of the securing element, such that when the second surface part faces the other of the first housing part and the second housing part, whereby said second surface part abuts against the other of the first housing part and the second housing part so that the securing element exerts a clamping force on the other of the first housing part and the second housing part, and such that when the first surface part faces the other of the first housing part and the second housing part the securing element exerts no or a minor clamping force on the other of the first housing part and the second housing part.

By means of such a securing element the second clamping part can easily be connected to and detached from the other housing part. In particular, the first surface part of the securing element is directed towards the other of the first housing part and the second housing part during the connection of the second clamping part with the other housing part, such that no or a smaller clamping force is exerted on the other of the first housing part and the second housing part, and wherein the securing element can then be rotated in a first direction of rotation to direct the second surface part to the other of the first housing part and the second housing part, so that the clamp exerts a clamping force or a greater clamping force for clamping the first housing part and the second housing part together, and contributing to an airtight seal therebetween. For loosening the clamp, the securing element can be rotated again in a second direction of rotation which is opposite to the first direction of rotation in order to direct the first surface part towards the other of the first housing part and the second housing part.

In particular, the distance from a surface of the securing element to the rotational axis from the first surface part along a circumference of the securing element can gradually and/or continuously increase to the second distance. The distance from a surface of the securing element to the rotational axis can be defined as the shortest distance from that surface to the rotational axis.

The surface can thereby be a circumferential surface, the first surface part and the second surface part being different parts of the circumferential surface.

In particular, the securing element can have a prismatic shape, in particular with an elliptical or circular base surface.

Even more particularly, the securing element can be a cylindrical securing element which is mounted eccentrically on the rotational axis.

The securing element may be provided with an impact element which abuts against the other of the first housing part and the second housing part when the second surface part abuts against the other of the first housing part and the second housing part, such that rotation of the securing element in the first direction is limited by the impact element so that, when the impact element abuts the other of the first housing part and the second housing part, further rotation in said first direction is not possible, and a rotation in the second direction opposite to the first direction is not counteracted by the impact element. In this case, the second surface part can lie against the other of the first housing part and the second housing part in such a way that the securing element does not automatically rotate in the second direction under the influence of a clamping force, but only rotates in the second direction when a for instance manual force is exerted.

In particular, rotation of the securing element, for alternately moving the first housing part and the second housing part towards the first surface part and the second surface part, can take place over an angular distance—considered from the rotational axis which is substantially equal to an angular distance between the first surface part and the second surface part.

In yet another embodiment of the centrifugal fan according to the invention, the securing element of the at least one clamp is fixedly connected to a lever for rotating the securing element.

A lever can facilitate the rotation of the securing element. In particular, the lever can enable rotation of the securing element by hand, even when a predominantly high coupling force is required to rotate the securing element. A high torque force may be desirable when a large clamping force of the clamp is required.

In yet another embodiment of centrifugal fan according to the invention, the at least one clamp comprises three clamps arranged over a circumferential zone of the first housing part and/or the second housing part.

By arranging three clamps over a peripheral zone, possibly together with a hinge, a clamping action can be distributed over the circumferential zone, which can contribute to an airtight seal.

In particular, the three clamps can also be arranged with an angular distance with respect to the hinge, whereby between the first housing part and the second housing part in the closed state of the centrifugal fan four connection zones distributed over the circumferential zone are defined.

In yet another embodiment of the centrifugal fan according to the invention, the first housing part and the second housing part are provided with mutually cooperating guiding means for guiding a mutual displacement.

As the guiding means guide a mutual displacement of the housing parts, it is not necessary that the full weight of the housing parts is supported by, for example, a user and/or the connecting means and/or the hinge cooperating with each other.

In particular, the cooperating connecting means and/or the hinge can hereby be relieved, whereby any deformation of these elements by weight of the housing parts can be prevented.

The mutual displacement may, for example, comprise translational and/or rotational displacement.

In another embodiment of the centrifugal fan according to the invention, the mutually cooperating guiding means comprise at least one support wheel rotationally connected to the one of the first housing part and the second housing part and at least one connected to the other of the first housing part and the second housing part and at least one wheel track connected to the other of the first housing part and the second housing part, wherein the wheel rolls against and/or in and/or on the wheel track when the centrifugal fan is set between its open and closed state.

The combination of at least one support wheel and at least one wheel track can be particularly advantageous if a housing part comprises other heavy components such as, for example, drive means such as, for example, a motor, whereby such a combination enables easy movement of the housing parts relative to each other, while the weight can be carried by the combination of wheel and wheel track instead of by, for instance, a user and/or the cooperating connecting means and/or the hinge.

In particular, the mutually co-operating guiding means comprise two support wheels.

In yet another embodiment of the centrifugal fan according to the invention, the housing comprises a sealing ring for sealing the housing in an airtight manner in the closed state.

The seal ring may contribute to an airtight seal of the housing in the closed state of the centrifugal fan.

In yet another embodiment of the centrifugal fan according to the invention, the sealing ring is made of one or more of: plastic, preferably silicone; and metal, preferably stainless steel, preferably stainless steel 301 according to the ASTM/AISI standard.

Such materials can be eminently suitable for airtight sealing of the housing, because they can have the right balance between hardness and elasticity.

Optionally, the sealing ring may be arranged at least partly in a groove in at least one of the two housing parts over its entire circumference. Still more particularly, the sealing ring may be arranged in the groove in such a way that the sealing ring is arranged in the groove with a first part of the entire circumference and protrudes from the groove with another part of its entire circumference. In particular, a stainless-steel sealing ring can be arranged at least partly in a groove in such a manner. In particular, the silicone sealing ring cannot be provided in a groove.

The invention also relates to a procedure for cleaning a centrifugal fan according to the invention, comprising the following steps: (a) setting the housing to the open state such that the periphery of the impeller and/or the inside of the housing are substantially fully accessible; (b) cleaning of the impeller and/or the inside of the housing; (c) setting the housing back to the closed state in which the housing connects the medium supply opening and the medium discharge opening to a medium-permeable and airtight one.

Such a procedure can have the advantage that the centrifugal fan can be cleaned easily, and is again airtight after cleaning. After cleaning, the centrifugal fan can therefore be more hygienic than centrifugal fans, that cannot or less be well cleaned and/or after opening cannot be closed airtight again.

In another embodiment of the procedure for cleaning a centrifugal fan according to the invention step (a) comprises rotating the securing element of the at least one clamp, from a first position whereby the second surface part is directed to the other of the first and second parts to a second position whereby the first surface part is directed to the other of the first and second parts, thus reducing at least the clamping force on the other of the first part; moving the second clamping part so that it is no longer connected to the other of the first housing part and the second housing part and comprises step (c) the setting of the housing to the closed state; connecting the second clamping part to the other of the first clamping part and the second clamping part; and rotating the securing element from at least one clamp, from the second position to the first position, thereby creating and/or increasing at least the clamping force on the other of the first clamping part.

Such a procedure can have the advantage that the fan can be set easily and/or quickly and/or manually and/or without other aids to its open state and closed state, and in particular can be closed airtight again after cleaning.

DESCRIPTION OF THE DRAWINGS

The invention will be further explained by means of the following figures, whereby:

FIG. 1 schematically shows a perspective front view of an embodiment of the centrifugal fan in a closed state according to the invention;

FIG. 2 schematically shows a perspective side view of the centrifugal fan of FIG. 1 in an open state;

FIG. 3 schematically shows a perspective rear view of the centrifugal fan of FIG. 1 in the closed state; and

FIG. 4 schematically shows a side view of a clamp of the centrifugal fan of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows a centrifugal fan 100 with a housing 1 enclosing an impeller 2. The centrifugal fan 100 in FIG. 1 is shown in a closed state, or a state of use. The impeller 2 is driven in this example by drive means 8. The housing 1 connects a medium supply opening 3 and a medium discharge opening 4 such that they are flowable connected to each other. When the impeller 2 rotates, the centrifugal fan 100 sucks media through the medium supply opening 3 and the centrifugal fan 100 blows media through the medium discharge opening 4. For the purpose of building up pressure and increasing hygiene, the housing 1 connects the medium supply opening 3 and the medium discharge opening 4 to one another in airtight manner. That means, a medium, for example air, which flows via the housing 1 from the medium supply opening 3 to the medium discharge opening 4, can only leave the housing through the medium discharge opening 4.

FIG. 2 shows the same centrifugal fan 100, in an open state. A circumference of the impeller 2 and an inside of the housing 1 are thereby accessible for instance for cleaning.

FIG. 3 shows the same centrifugal fan 100, in the closed state of FIG. 1, but from a different side thereof.

It is noted that front view, rear view and side view are chosen randomly and that, for example, it may be that the front view is actually a rear view.

The housing 1 of the centrifugal fan 100 of FIGS. 1 and 2 comprises in this example a first housing part 5 and a second housing part 6, both of which are arranged substantially perpendicular to a rotational axis R1 (see FIG. 2) of the impeller 2. This means that at least one main surface of each housing part 5, 6 is arranged substantially perpendicular to the rotational axis R1. In this example, one of the two housing parts, in this case the first housing part 5, comprises a circumferential wall 7, which in the closed state of FIG. 1 connects the first housing part 5 and the second housing part 6 in airtight manner. The circumferential wall 7 extends in the closed state of FIG. 1 substantially parallel to the rotational axis R1 around it between the main surfaces of the housing parts 5, 6. The first housing part 5 and the second housing part 6 are separated from each other in the open state shown in FIG. 2, so that the inside of the housing 1 and in any case the circumference of the impeller 2 are accessible. The housing 1, in this case the second housing part 6, is provided with a sealing ring 29 along a complete circumferential zone of the second housing part 6, whereby the circumferential zone, via the sealing ring 29, in the closed state of the centrifugal fan 100 is in contact with a head circumferential end of the circumferential wall 7 directed towards the second housing part 6. The sealing ring 29 lies at least partly in a groove (not visible) in the second housing part 6 over its entire circumference, and in this case extends at least partly over its entire circumference. In this embodiment the sealing ring is made of a stainless steel, in particular of stainless steel 301 according to the ASTM/AISI standard.

In this example, the first housing part 5 and the second housing part 6 are connected to each other by a hinge 9, as shown in for instance FIG. 3. In this case the hinge 9 comprises a pole element 10 connected to the second housing part 6, which together with the second housing part 6 is rotatable in relation to the first housing part 5 and mounted by means of rotary bushes 11, 11′ at its top and bottom. The pole element 10 is provided with a reduced shaft journal (not visible) at least one of its end zones. Spacer sleeves can be placed around the reduced shaft journal for adjusting the pole element 10 in length. In this example, the pole element 10 is attached to the second housing part 6 by means of two bolt connections 12. The bolt connections 12 are adjustable, whereby the distance and to some extent the orientation of the pole element 10 to and/or relative to the second housing part 6 can be adjusted. The pole element 10 is attached to the first housing part 5 by means of the upper rotary bushing 11′ via adjustment plates 13, which are adjustable relative to each other because bolts 14 are mounted in slots (not visible). The adjustment plates 13 are kept separate from each other by spacer sleeves 15 (best seen in FIG. 1). By means of adjustable fastening means, which can comprise the bolt connections 12, adjusting plates 13 and longitudinally adjustable pole element 10, the hinge 9 is adjustable with respect to both housing parts 5, 6. In FIG. 3 it is furthermore visible that the first housing part 5 and the second housing part 6 are provided with guide means 27, 28 cooperating with each other. In this case, the cooperating guiding means 27, 28 comprise two support wheels 27 which are rotatably connected to the second housing part 6. The support wheels 27 can, when the centrifugal fan 100 is set from being closed to its open state and/or the other way around, roll over wheel tracks 28 which are fixedly connected to the first housing part 5. As a result, the support wheels 27 and wheel tracks 28 can together absorb a part of the force exerted by the second housing part 6 on the first housing part 5, for instance by the weight of drive means 8.

The first housing part 5 and the second housing part 6 are provided with mutually cooperating connecting means, in this case clamps 16, 16′ and lips 17, 17′. FIGS. 1 and 2 show that the centrifugal fan 100 comprises a total of three clamps 16, 16′ and associated lips 17, 17′. Two clamps 16 are attached to the first housing part 5 with their associated lips attached to the second housing part 6, and one clip 16′ is attached to the second housing part 6, with its associated lip 17′ being fixed to the first housing part 5 (best visible in FIG. 1). The three clamps are arranged spread over the circumference of centrifugal fan 100, and are all arranged at a certain angular distance from the hinge 9, viewed from the rotational axis R1. In FIG. 4, a clamp 16 is shown in more detail. The clamp 16 comprises a first clamping part 18 which is fixedly connected to the first housing part 5. In this case, the first clamping part 18 comprises a hinge, through which an elongate body 20 can pivot relative to the first housing part 5. The clamp 16 also comprises a second clamping part 19. The elongate body 20 extends between the first clamping part 18 and the second clamping part 19 and connects the two clamping parts 18, 19. The second clamping part 19 can, as shown by solid lines, be connected to the second housing part. The same clamp 16 is shown in dotted lines, whereby the elongate body 20 and thereby the second clamping part 19 are pivoted away from the second housing part 6, whereby the second clamping part 19 is detached from and thus not connected to second housing part 6. The elongate body 20 in this example is connected to the first clamping part 18 by means of, inter alia, adjusting nut 21 and saucer spring 22 (not visible in FIG. 4) which abuts against adjusting nut 21. By adjusting the adjusting nut 21 the distance between the first clamping part 18 and the second clamping part 19 can be changed and thereby a clamping force can be adjusted. The second clamping part 19 comprises in this example a securing element 23, which in this example is a securing cylinder 23. The securing cylinder 23 is rotatably mounted about a rotational axis R2 and comprises a first surface part 24 and a second surface part 25. A first distance from the first surface part 24 to the rotational axis R2 of the securing cylinder 23 is smaller than a second distance from the second surface part 25 to the rotational axis of the securing cylinder 23. In other words, in this case the securing cylinder 23 is mounted eccentrically. With solid lines is shown how securing cylinder 23, in particular with the second surface part 25, abuts the second housing part 6 in the closed state of the housing, so that the clamp 16 clamps the two housing parts 5, 6 towards each other. A lever 26 is provided on the securing cylinder 23, which lever 26 in this example can be used as a handle for rotating the securing cylinder 23. With the aid of the lever 26, the securing cylinder can be rotated between a first position, in which the securing cylinder with its first surface part 24 is directed towards the second housing part 6, and a second state in which the securing cylinder with its second surface part 25 is directed towards the second housing part 6. From the first state to the second state, the securing cylinder rotates in a first direction, and from the second state to the first state in a second direction, the second direction being opposite to the first direction. The lever 26 furthermore has an impact element 31 which abuts against the second housing part 6 when the securing cylinder 23 abuts the second surface part 25 against the second housing part 6, so that the securing cylinder cannot rotate further in the first direction.

Clamp 16′ can be designed substantially equal to the clamp 16 of FIG. 4. For a description thereof, reference is also made to FIG. 4, wherever there is first housing part 5, this must be the second housing part 6 for the clamp 16′ and vice versa.

It is noted that the rotational axis R1 and the rotational axis R2 are imaginary axes about which the impeller 2 and the securing element 23 respectively rotate.

It is to be noted that the invention is not limited to the embodiments shown, but also extends to variants within the scope of the appended claims. In this regard, the securing cylinder 23 can be incorporated into the lever 26 itself, at the end of the lever 26 that rotates about axis R2. As a further example the securing cylinder and handle could be replaced by an over-center latch. Moreover the overcenter latch can be constructed to be adjustable in a know manner so that the clamping force exerted by the latch can be adjusted as desired. 

The embodiments of the invention in which an exclusive property or priviolege is claimed are defined as follows:
 1. A centrifugal fan comprising: an impeller, a housing enclosing at least the impeller with a medium supply opening and a medium discharge opening, wherein the housing configured to connect the medium supply opening and the medium discharge opening to a medium-permeable and airtight manner, and wherein the housing is adjustable between an open state, wherein at least one circumference of the impeller and/or the inside of the housing is substantially completely accessible and it's a closed state, wherein the housing connects the medium supply opening and the medium discharge opening to a medium-permeable and air-tight manner.
 2. A fan according to claim 1, wherein: the impeller is rotatable about a rotational axis, wherein the housing comprises a first housing part arranged on a first side of the impeller perpendicularly to the rotational axis and comprises a second housing part arranged on a second side of the impeller perpendicular to the rotational axis, wherein the first housing part and/or the second housing part comprising a circumferential wall which in the closed state of the centrifugal fan connects the first housing part and the second housing part in an airtight manner, and wherein the first housing part and the second housing part being separable from each other for adjusting the centrifugal fan to its open state.
 3. A centrifugal fan according to claim 2, wherein the first housing part and the second housing part are pivotally connected to each other.
 4. A centrifugal fan according to claim 3, wherein the pivotal connection of the first housing part to the second housing part comprises a hinge connected to the first housing part and/or the second housing part.
 5. A centrifugal fan according to claim 2, wherein the first housing part and the second housing part are provided with mutually cooperating connector for connecting the first housing part and the second housing part together.
 6. Centrifugal fan according to claim 5, wherein the cooperating connecting means comprising at least one clamp, which at least one clamp is provided with: a first clamp part which is fixedly connected to one of the first housing part and the second housing part, and a second clamping part which is detachably connectable to the other of the first housing part and the second housing part, wherein: in the opened state of the centrifugal fan the second clamping part is not connected to the other of the first housing part and the second housing part, and in the closed state of the centrifugal fan the second clamping part is connected to the other of the first housing part and the second housing part; and the clamp clamps the first housing part and the second housing part towards each other by means of the first clamping part and the second clamping part.
 7. Centrifugal fan according to claim 6, wherein a distance between the first clamping part and the second clamping part of the clamp is adjustable for adjusting a clamping force with which the clamp clamps the first housing part and the second housing part towards each other in the closed state of the centrifugal fan.
 8. Centrifugal fan according to claim 6, wherein the at least one clamp is provided with a spring element which in the closed state of the centrifugal fan is arranged for supplying a clamping force by preloading a clamping force for clamping the first housing part and the second housing part towards each other, wherein the spring element is preferably a saucer spring.
 9. Centrifugal fan according to claim 6, whereby the second clamping part comprising a securing element rotatable about a rotational axis, whereby the securing element, in a closed state of the centrifugal fan, abuts against the other of the first housing part and the second housing part for clamping the first housing part and the second housing part towards each other, whereby the securing element comprises a first surface part remote with a first distance from the rotation axis and a second surface part remote with a second distance from the rotational axis, whereby the first distance being smaller than the second distance, whereby the first surface part and second surface part can be alternately directed towards the other of the first housing part and the second housing part by rotation of the securing element, whereby said second surface part abuts against the other of the first housing part and the second housing part so that the securing element exerts a clamping force on the other of the first housing part and the second housing part, and such that when the first surface part faces the other of the first housing part and the second housing part the securing element exerts no or a minor clamping force on the other of the first housing part and the second housing part.
 10. Centrifugal fan according to claim 9, wherein the securing element is of the at least one clamp is fixedly connected to a lever for rotating the securing element.
 11. Centrifugal fan according to claim 6, wherein the at least one clamp comprises three clamps arranged over a circumferential zone of the first housing part and/or the second housing part.
 12. Centrifugal fan according to claim 2, wherein the first housing part and the second housing part are provided with a mutually cooperating guide for guiding a mutual displacement and/or rotation.
 13. Centrifugal fan according to claim 12, wherein the mutually cooperating guide comprising at least one rotatable support wheel connected to one of the first and second housing parts and at least one wheel track connected to the other of the first and second housing part, whereby the wheel rolls against and/or in and/or on the wheel track when the centrifugal fan is set between its open and closed state.
 14. Centrifugal fan according to claim 1, whereby the housing comprises a sealing ring for airtight sealing of the housing in the closed state.
 15. Centrifugal fan according to claim 14, whereby the sealing ring is made of one or more: plastic, preferably silicone; and metal.
 16. A procedure for cleaning a centrifugal fan constructed according to claim 1, comprising: (a) setting the housing to the open state such that the circumference of the impeller and/or the inside of the housing are substantially completely accessible; (b) cleaning of the impeller and/or the inside of the housing; (c) the setting of the housing back to the closed state whereby the housing connects the medium supply opening and the medium discharge opening to a medium-permeable and air-tight manner.
 17. A procedure for cleaning a centrifugal fan constructed according to claim 2, comprising: (a) setting the housing to an open state such that the circumference of the impeller and/or the inside of the housing are substantially completely accessible by rotating the housing first part relative to the housing second part to provide accessibility to the impeller and/or the inside of the housing; (b) cleaning the impeller and/or inside of the housing; and (c) setting the housing back to a closed state whereby the housing connects a medium supply opening to the housing and a medium discharge opening from the housing to a medium-permeable and air-tight state by rotating the housing first part relative to the housing second part back to their initial closed state. 